It is well recognized that ultra-high precision assembly or manufacturing, typically requiring up to 10 nanometers linear resolution, is of strategic importance to industrial processes such as optoelectronics assembly, precision machining, and semiconductor manufacturing. In such processes, both the machine dynamics and operating environment are critical to the quality of the end product. "Hard" nonlinearities such as surface friction, backlash, and hysteresis are generally difficult to predict and to compensate for, resulting in significant degradation of the process performance.
To eliminate thread friction and wear and provide damping on the axis of motion, hydrostatic and aerostatic leadscrews have been used to replace conventional ball or roller leadscrews in manufacturing machines. For example, at least one known device utilizes a hydrostatic leadscrew for behind-the-wheel dressing system with a claimed resolution of 10 nanometers. Satomi studied the use of aerostatic leadscrew as a positioning and guiding system for machine tools. See "Studies on aerostatic lead screws," T. Satomi, World Congress of IFToMM, 1987, pp. 1545-1548. These approaches use pressurized fluids to separate enmeshed, i.e., mechanically coupled, threads.
On the other hand, magnetic coupling has also been investigated for achieving contactless drives. For example, Kikuchi and Tsurumoto experimented with a permanent magnet worm gear. See "Design and characteristics of a new magnetic worm gear using permanent magnet," IEEE Trans. on Magnetics, Vol. 29, No. 6, 1993, pp. 2923-2925. Various other linear actuators are described in the following patents, all of which are incorporated herein in their entirety: U.S. Pat. No. 3,777,587 issued to Hoshina et al.; U.S. Pat. No. 3,824,420 issued to Stegeman et al.; U.S. Pat. No. 4,123,691 issued to Seilly; U.S. Pat. No. 4,145,625 issued to Seilly; U.S. Pat. No. 4,214,180 issued to Kuwako et al.; U.S. Pat. No. 4,439,702 issued to Belikov et al.; U.S. Pat. No. 4,712,027 issued to Karidis; U.S. Pat. No. 4,734,605 issued to Hayashi; U.S. Pat. No. 4,920,292 issued to Albrecht et al.; and U.S. Pat. No. 5,099,161 issued to Wolfbauer, III.
Therefore, it is a principal object of the present invention to provide a means of generating high or ultra-high precision movement
It is another object of the present invention to provide a means of generating high or ultra-high precision movement based on the principle of magnetic traction and aerostatic suspension.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.